The present invention provides a system for mounting a head-up display system in the cockpit of an aircraft so that the display may be moved in a generally vertical direction between a plurality of positions to accommodate pilots of different heights.
Head-up displays, or HUDs, are displays that allow pilots to view critical flight information superimposed on the real world view out the front of the aircraft, rather than looking down at the instrument panel. HUDs typically have several components, including a computer, an overhead optical unit, and a combiner. The computer processes information input from various aircraft sensors and systems and outputs signals for display. The optical unit creates and projects an image of the processed information. It is generally mounted above the pilot""s or copilot""s seat, and typically includes a cathode-ray tube to create the image, electronics to drive the cathode ray tube, and a lens system to project the image onto the combiner. The combiner is an optically powered element positioned between the pilot""s eyes and the aircraft windshield that reflects only a narrow band of light, and transmits most other wavelengths from the rear world to the pilot. Thus, it both reflects the image from the CRT toward the pilot and transmits light from outside the cockpit, combining the projected image with the view outside the cockpit. The combiner focuses the reflected display at infinity, so a pilot""s eyes do not need to refocus when switching between the combiner display and the outside view, and there is no relative motion of the display with respect to the real world with head movement.
HUDs are becoming increasingly popular on all kinds of aircraft, including commercial, corporate and military aircraft, due to the wide variety of flight information that may be displayed. For example, while some HUDs simply repeat flight information already available on the instruments in the panel, others display complex flight path information calculated from inertial data generated by inertial laser reference sensors on the aircraft. Commonly displayed parameters include the boresight, or an extension of the aircraft longitudinal axis, the velocity vector, or the direction of the aircraft, the horizon, the actual and selected airspeeds, the ground speed, the actual and selected altitudes, the magnetic compass heading, and the pitch and roll of the aircraft.
Initially, HUDs were installed because they offered significant enhancements to aircraft capability. For example, delays and cancellations due to poor visibility are a significant cause of revenue loss for commercial airlines. Planes equipped with HUDs often qualify for lower visibility takeoffs and landings compared with non-equipped planes. Thus, these planes may have fewer weather delays and flight cancellations, and may reduce revenue losses due to weather. Similarly, military aircraft equipped with HUDs are able to fly missions in worse weather than non-equipped planes, thus offering both strategic and financial advantages in military applications.
More recently, HUDs are used to enhance aircraft safety by improving pilot situational awareness. For example, in takeoff and landing phases of flight, pilot situational awareness is increased through the use of HUDs. Furthermore, some newer HUDs include advanced features such as unusual attitude recovery symbology mode, tailstrike warnings and traffic-alert and collision avoidance capabilities to help a pilot avoid or recover from hazardous situations.
Because of the capability and safety enhancements offered, HUDs are being installed in many new aircraft and retrofitted in many existing aircraft. The HUD information is visible from within a volume of space known as the eyebox. To achieve the maximum safety and capability benefits, the HUDs generally should be installed in a cockpit so that the eyebox is centered at the cockpit design eye point, or the DEP. The DEP is an ergonomically determined eye position that is the optimal location in the cockpit for viewing both instruments and objects outside of the plane through the windshield. Thus, positioning the HUD eyebox at the DEP helps to optimize the pilot""s view of the HUD while not compromising the view of both the outside world and the instruments on the panel.
Generally, aircraft cockpits are designed with adjustable seats so pilots of different heights can locate themselves at the DEP. Moreover, some older aircraft were not designed to accommodate the full range of male and female pilot populations. In some cases, seats may not travel far enough up or down to position the pilot""s eye close enough to the DEP for the pilot to be centered within the HUD eyebox. A pilot that is not able to reach the center of the HUD eyebox will not be able to view all of the HUD display without head motion, and will not be able to take full advantage of the safety benefits offered by the HUD. This limits the number of pilots that may operate the aircraft using the HUD, and thus lowers the capability of the aircraft. Furthermore, some modem aircraft use HUDs as the primary flight display in the aircraft. Pilots who cannot reach the eyebox may be restricted from flying these planes.
One solution to this problem is to replace the cockpit seats with seats that have a greater range of height adjustment. However, this method can pose problems when retrofitting older planes with HUD equipment. For example, the yokes and rudder pedals in many older planes are designed to accommodate the range of heights of the seats originally installed in the plane. If seats with a greater range of heights are installed, the yokes and pedals may have to be moved or replaced to accommodate the greater range, significantly increasing the cost of the retrofit.
Therefore, there remains a need for a system for installing a head-up display system in an aircraft cockpit that allows the display system to be viewed by pilots of a wide range of heights, yet does not require expensive modifications to the aircraft cockpit.
One aspect of the present invention provides a system for mounting a head-up display in a cockpit of an aircraft, the cockpit including a front region and a back region, the head-up display including a computer adapted to process flight information, an optical unit adapted to project an image corresponding to the flight information processed by the computer, and a combiner adapted to display the image projected by the optical unit. The system comprises a frame with a front region and a back region, the frame including an optical unit interface for mounting the optical unit and a combiner interface for mounting the combiner, wherein the frame is adapted to be movably coupled to the cockpit such that the frame may be moved in a generally vertical direction between a plurality of positions relative to the cockpit. The system also includes at least one sensor coupled to the frame, wherein the sensor senses the position of the frame and provides a signal to the computer corresponding to the position of the frame so that the computer may adjust at least part of the image displayed on the combiner to correspond to the position of the frame.
Another aspect of the invention provides an aircraft, the aircraft including a cockpit and the cockpit including a head-up display system. The head-up display system comprises a frame movably mounted to the aircraft in the cockpit, wherein the frame may be moved in a generally vertical direction between a plurality of positions relative to the cockpit, a computer disposed in the aircraft, wherein the computer is configured to process aircraft flight data, an optical unit mounted to the frame, wherein the optical unit is configured to project an image corresponding to the processed flight data, and a combiner mounted to the frame, wherein the combiner is adapted to display the image projected by the optical unit. The head-up display system also includes at least one sensor coupled to the frame, wherein the sensor is adapted to sense the position of the frame and to provide a signal to the computer so that the computer may adjust the image to correspond to the position of the frame.
Yet another aspect of the present invention provides a method of installing a head-up display unit in a cockpit of an aircraft, the display unit including a frame, an optical unit for projecting an image of flight information, a combiner for displaying the image, and a computer, and the frame including a movable coupling structure and at least one electronic offset circuit to characterize a frame offset. The method comprises (1) establishing a reference direction for the head-up display; (2) positioning an alignment reference such that the alignment reference is in a position in front of the aircraft along the reference direction; (3) installing at least one mounting bracket in the cockpit; (4) positioning the frame in the mounting bracket such that the movable coupling structure is at a position adjacent the mounting bracket; (5) attaching a frame alignment tool to the frame; (6) comparing the position of the frame and the position of the alignment reference using the frame alignment tool; (7) moving the frame until the frame is in a coarse alignment with the alignment reference; (8) fixing the movable coupling structure to the support bracket such the frame may be moved in a generally vertical direction between a plurality of vertical positions relative to the cockpit, but may not be moved in other directions; (9) obtaining a first offset value that characterizes a misalignment of the frame relative to the boresight direction while the frame is in a first vertical position, and adjusting the offset circuit to correspond to the first offset valve; (10) storing the first offset valve in the computer; (11) moving the frame to a second position; (12) obtaining a second offset value that characterizes the misalignment of the frame at the second vertical position and adjusting the offset circuit to correspond to the second offset valve; (13) storing the second offset valve in the computer; (14) detaching the frame alignment tool from the frame; and (15) attaching the combiner and optical unit to the frame.